The present invention relates to a liquid crystal projector, in particular, to a liquid crystal projector which has liquid crystal panels fixed to a dichroic prism under improved fixation configuration.
Generally, a liquid crystal projector includes a plurality of liquid crystal panels for modulating red (R), green (G), and blue (B) lights respectively, a dichroic prism for compositing thus modulated R, G, and B lights to generate a color image, and an optical system such as a projection lens for magnifying and projecting thus generated color image.
In a liquid crystal projector of this kind, respective color lights modulated by a plurality of liquid crystal panels are composited by a dichroic prism. So as to align pixels of respective liquid crystal panels to superpose projected images generated by respective liquid crystal panels onto a screen with high accuracy, such a liquid crystal projector is required to have an adjustment mechanism along the upward and downward, leftward and rightward, and rotation direction. Also, an adjustment mechanism for focusing along the forward and backward, pitching, and yawing direction is necessary so as to accurately bring focal points of projected images onto a screen into focus. In case of an optical prism unit having such adjustment mechanisms united therein, it becomes difficult to reduce the adjustment mechanisms in size when the size of liquid crystal panels is smaller than is predetermined. The more adjustment mechanisms become accurate for fine adjustment, the larger the adjustment mechanisms become in size. Thus, even though liquid crystal panels themselves are reduced in size, it is difficult to reduce an optical prism unit itself and a liquid crystal projector itself in size in view of their configuration under the constraint in size of their adjustment mechanisms. There is proposed a liquid crystal projector which has liquid crystal panels directly adhered to be fixed to a dichroic prism, excluding above-described adjustment mechanisms for the purpose of miniaturization. However, in case defect is detected in a liquid crystal panel, it is difficult to exchange only the defective liquid crystal panel after adhering the liquid crystal panel to a dichroic prism. So, even though defect is detected in only one liquid crystal panel, a unit of dichroic prism including the defective liquid crystal panel as well as other non-defective liquid crystal panels has to be exchanged, which is not economic.
There is also proposed a liquid crystal projector which has a panel fixation frame fixed to a dichroic prism, and has liquid crystal panels fixed to the panel fixation frame, excluding adjustment mechanisms from an optical unit. In this case, the liquid crystal projector is provided with a space or an air gap between the emergent surfaces of the liquid crystal panels and the incident surfaces of a dichroic prism. In the air gap, polarizing plates of the emergent sides are also provided. Thus, there is raised a problem that dust, which is scattered by a cooling fan for cooling liquid crystal panels, may break into the air gap and stick to the polarizing plates and the liquid crystal panels. Dust which is larger than is predetermined against the pixel size has a bad influence on the quality of projected images. The smaller the liquid crystal panels become, the more the problem of dust becomes serious.
As a liquid crystal panel is miniaturized, the density of an incident light from a light source increases, which subsequently increases the operation temperature of the liquid crystal panel. Furthermore, as a liquid crystal projector is miniaturized, an optical prism unit is also required to be miniaturized. In this case, it is predicted that the operation temperature undesirably exceed the top temperature limit under which emergent-side polarizing plates and liquid crystal panels cannot operate, which problem should be definitely solved. In a liquid crystal projector, polarizing plates located at the emergent sides and liquid crystal panels absorb lights from light sources and generate heat. Such polarizing plates and liquid crystal panels are made of organic material, and it is required that the operation temperature thereof be suppressed under 70xc2x0 C. in enhancing the credibility of the operation of a liquid crystal projector.
Accordingly, the present invention has an object to overcome the above-mentioned drawbacks of the prior art by providing a liquid crystal projector which has liquid crystal panels fixed to a prism under improved fixation configuration, which enables exchange of parts or elements easily, and has sufficient capability of radiating heat, and can also prevent sticking of dust.
The above object can be attained by providing a liquid crystal projector including a plurality of liquid crystal panels for modulating a plurality of color lights respectively, a prism for compositing thus modulated plural color lights to generate a color image, and an optical system for magnifying and projecting thus generated color image, wherein the liquid crystal panels are directly adhered to metal hold plates, and the metal hold plates are fixed to the prism such that the emergent surfaces of the liquid crystal panels face the incident surfaces of the prism. The liquid crystal panels preferably have glass sheets having thermal conductivity fixed to the incident surfaces thereof. Radiation fins are fixed to the prism with the metal hold plates and the glass sheets having thermal conductivity brought into contact with the fins. A closed space is provided between the incident surfaces of the prism and the emergent surfaces of the liquid crystal panels so as to prevent air flow, and at least polarizing plates are arranged in the closed space. The polarizing plates are arranged at the incident sides of the prism, and thermal conduction members for absorbing heat generated in the polarizing plates may be arranged in the closed space.
According to the liquid crystal projector of the present invention, the liquid crystal panels are directly adhered to metal hold plates, and the metal hold plates are fixed to the prism such that the emergent surfaces of the liquid crystal panels face the incident surfaces of the prism. By employing this configuration, an optical prism unit united with liquid crystal panels can be reduced in size, and can be exchanged easily when defect is detected in a liquid crystal panel. The liquid crystal panels, which are directly adhered to metal hold plates excellent in thermal conductivity, are excellent in heat radiation. Furthermore, the liquid crystal panels have glass sheets made of such as sapphire glass having thermal conductivity fixed to the incident surfaces thereof. Also, radiation fins are fixed to the prism with the metal hold plates and the glass sheets having thermal conductivity brought into contact with the fins. By employing this configuration, the liquid crystal panels can be efficiently cooled. In addition, a closed space or an air gap is provided between the incident surfaces of the prism and the emergent surfaces of the liquid crystal panels so as to prevent air flow, which can prevent dust from breaking into the air gap and sticking to the polarizing plates and the liquid crystal panels arranged therein.
These objects and other objects, features and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments of the present invention.